In any closed gas system having working areas where vaporized contaminants can condense and cause difficulties, it is desirable to remove those contaminants or to condense them out at a point or at points where they do not deleteriously affect the operation of the system. Gas bearings frequently involve the use of closed gas systems and are particularly subject to problems arising from contaminant deposition in critical areas. In most gas bearings, the adjacent faces of a normally stationary element and a normally rotatable element have matching contours and are assembled closely together leaving only a narrow space between the two as a bearing gap to accommodate the bearing gas.
In sealed instruments containing a float gas, the gas at the float ambient pressure may be captured and caused to flow inwardly at increasing pressure toward the bearing gap by grooves or similar geometric configurations formed adjacent the bearing gap on one of the confronting surfaces of the stationary or rotating elements. One design for achieving such bearing pressures in floated gyros is known as the Whipple spiral, grooves being formed on the surfaces of such elements as the thrust pads or the shaft about which the inertial element of the gyro turns.
Although the basic hydrodynamic gas spin bearing theory is sound and various systems for introducing gas at relatively high pressure into the bearing gap have performed adequately, certain practical problems have been encountered. One of the more common difficulties derives from the fact that vaporized contaminants are inevitably present in the bearing gas. In the particular case of floated gyros, the contaminants may emanate from many sources, including the housing and components of the instrument but especially from the organic insulating material, cements, and impregnants used in the manufacture of the stator of the drive motor commonly used in gyro instruments. Condensation of these contaminants takes place in or adjacent to the bearing gap because the ability of the float gas to retain contaminants in a vaporized state is substantially lowered in those areas where the gas is at high pressure as compared to other areas of low pressure such as those at ambient float gas pressure. In gas bearing systems, the obvious result of the condensation of such foreign material is short bearing life.
Similarly, the deposition or condensation of vaporized contaminants in critical working areas of other closed gas systems is a source of trouble and shortened life. The present invention has as its general object the elimination of vaporized contaminants from closed gas systems by compression/expansion techniques. A more specific object and application of the invention concerns the extension of gas bearing life by the reduction of damage and failure caused by condensation of vaporized contaminants in the bearing gap.